Labour's Rachael Maskell revealed she had been advised by the NHS 111 helpline to self-isolate following a meeting with Ms Dorries last Thursday, even though she is displaying no symptoms of COVID-19.

She told Sky News she would continue her work as an MP by holding meetings over the phone, adding: "This will become a norm over the coming weeks and days as we are seeing more people being diagnosed with coronavirus."

Ms Dorries, the minister in charge of patient safety, said in a statement that she "took all the advised precautions and have been self-isolating at home" since being informed she had tested positive.

"Public Health England (PHE) has started detailed contact tracing and the department and my parliamentary office are closely following their advice," she said.

"I would like to thank PHE and the wonderful NHS staff who have provided me with advice and support."

She added in a tweet: "It's been pretty rubbish but I hope I'm over the worst of it now. More worried about my 84yo mum who is staying with me and began with the cough today. She is being tested tomorrow."

Ms Dorries has also sent a message on the WhatsApp group for Tory MPs to ask them to get in touch if they were in contact with her.

The MP first showed symptoms on Thursday - the same day she attended the Downing Street event hosted by Mr Johnson to mark International Women's Day, according to a health department spokesman.

Image:Ms Dorries spoke in Westminster Hall on 5 March

Ms Dorries has voted twice in the House of Commons in the past week, according to parliamentary records - likely meaning she has been in close contact with hundreds of MPs.

She also spoke in a debate on eating disorders in Westminster Hall, on the parliamentary estate, last Thursday.

However, there are currently no plans to suspend parliament.

The 62-year-old also met people at a constituency surgery in Bedfordshire on Saturday.

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Health Secretary Matt Hancock said he was "really sorry" to hear the news but that "she has done the right thing by self-isolating at home".

Sky News' political editor Beth Rigby said that "as a health minister in contact with other health ministers and officials the obvious question is whether there has been wider transmission in Department of Health team".

"I understand Matt Hancock is in good health and not displaying any symptoms," she added.

Politicians from across the political divide sent messages wishing Ms Dorries a swift recovery.

Labour shadow cabinet member Luke Pollard tweeted: "Politics should not get in the way of being decent human beings to one another."